In the development of improved television systems, especially in the projection field, it has been found that reflective liquid crystal displays (LCD) or liquid crystal on silicon (LCOS) has been found to have attributes for high resolution in large screen digital displays. Because the display is fabricated on silicon, LCOS displays have the ability to create small pixel size and high-resolution. Such reflective displays have a large pixel aperture ratio which results in a smooth and continuous image especially suitable for display of natural images and video. The development of a single panel color projection video display enables the creation of a color image without the ⅔ light loss associated with a conventional color wheel system by keeping all colors on the display panel at all times.
The continuous scrolling action of differently colored stripes, usually red, green and blue, are such that as a stripe leaves the bottom of the display panel the stripe is split and discontinuously redirected to the top of the panel. Concurrently with this optical scan an electrical scan is provided which addresses the rows of pixels with a signal corresponding to the color of the light impinging on the pixel row. The sequence of light bands passing over the display panel occurs so quickly as to give the viewer an appearance of simultaneous full color.
In such video systems wherein digital video samples are converted to analog voltages, and then sampled into the pixel array, the number of gray scale levels is limited by the dynamic range of the video digital to analog conversion. The present invention is directed to overcoming one or more of the problems or disadvantages associated with the relevant technology.
In the method of this invention, the number of gray scale levels in an image is increased without increasing the dynamic range of the digital to analog conversion. In one embodiment of this method such an increase is effected by separating each pixel into two or more time-displaced samples that are presented to the display panel in synchronization with appropriate illumination. For example, the number of gray levels in a system utilizing 8-bit to 12-bit pixels can be increased from 256 steps to 4,096 steps by using an 8-bit digital to analog conversion. Such a technique would be very useful in cinema, medical and advanced CAD applications. The present invention addresses one or more of these concerns.